Ethernet Virtual Private Tree (E-TREE), or rooted point-to-multipoint Ethernet Virtual Connection (EVC), is a Layer 2 service defined by the Metro-Ethernet Forum (MEF) that provides an Ethernet virtual local area network (VLAN) configuration suitable for multicast services. Illustratively, the Internet Engineering Task Force (IETF) Internet Draft entitled “Requirements for MEF E-Tree Support in VPLS”<draft-ietf-12vpn-etree-reqt> by Key et al. specifies the requirements for supporting MEF E-TREE service in layer-2 virtual private network (L2VPN). Other types of EVCs defined for Carrier Ethernet networking are the E-Line and E-LAN.
The sites in an E-TREE service have constrained connectivity, and are designated as being Root and/or Leaf. The service is set up such that:                Root sites can communicate with all other sites (Root or Leaf).        Leaf sites can communicate with Root sites, but not with other Leaf sites.        
All solutions for addressing E-TREE in L2VPN (whether for virtual private LAN service (VPLS), Virtual Private Multicast Service (VPMS) or Ethernet Virtual Private Network (EVPN)) rely on an egress-filtering model. This means that the egress (i.e., disposition) provider edge (PE) device decides on whether to forward or drop traffic destined to a local attachment circuit, to satisfy the E-TREE connectivity constraints. This model unnecessarily wastes the bandwidth of the Multi-Protocol Label Switching (MPLS) network, where leaf-to-leaf traffic, all known unicast traffic, and ingress-replicated multi-destination traffic (broadcast, unicast unknown, and multicast (BUM) traffic), is transported over the MPLS network only to be dropped on the egress PE.